Mechanic's creepers are in wide-spread use, however, it has been found that the common, prior art mechanic's creeper design can be improved in a number of ways. Currently, mechanic's creepers are designed with side rails usually of rectangular or square cross section. The side rails thus provide sharp edges that lie adjacent to the padding held between the side rails. Because the padding sections provided between the side rails are not normally as wide as the breadth of the shoulders of the typical user, the sharp edges can often present a discomfort to the user.
Also, the casters on the typical mechanic's creeper are attached to the side rails in such a way as to provide protrusions on the top surface of the side rails. These protrusions can be an additional source of discomfort to the user because they are likely to snag and tear the user's clothing and scratch the user's body. More specifically, in mechanic's creepers of the prior art, the casters are attached to the side rails by means of a caster-carrying stud that is inserted through both the top and bottom walls of the side rail and secured by a nut threaded thereon. The remainder of the caster assembly is thereby positioned below the side rail and a bolt-head protrusion is undesirably located on the top surface of the side rail.
The width of the side rails in mechanic's creepers of the prior art relative to the diameter of the caster raceways needed to support the creeper also presents problems. Prior art mechanic's creeper designs incorporate caster assemblies having bearing races that are of larger diameter than the width of the side rails such that a portion of the bearing race extends beyond the sides of the side rails. As such, the portion of the bearing race which extends beyond the side rails is susceptible to being bumped or otherwise contacted, which could readily loosen or otherwise damage the caster assembly. Moreover, since the bearing race does not fully engage the side rail all the way around the race, the rocking forces born by the caster assemblies as the mechanic's creeper is utilized create weaknesses in the caster assemblies. For instance, the nuts securing the bolts through the side rails tend to loosen due to the torque placed upon the stem of the bolt as the creeper is moved and the caster assemblies roll and change directions. Moreover, adverse forces on the caster stems may well cause a shearing of these stems. In addition, because the bearing races do not completely engage the side rails, the weight placed upon the mechanic's creeper (i.e., the weight of the user's body) is not evenly distributed to the bearing race and the bearings therein. This increases the wearing of the bearings and therefore shortens the useful life of the caster assemblies and the mechanic's creeper as a whole.
The wheels used in the caster assemblies of prior art mechanic's creepers are also in need of improvement. In the prior art, the wheels of a mechanic's creeper generally contact the ground with a wide, flat bottom surface area. This design maximizes the amount of friction between the wheel surface and the ground surface on which the creeper rests. Mechanic's creepers are designed to be capable of moving in any direction and, thus, excessive friction between the caster wheels and the ground surface is counterproductive to the mobility of the mechanic's creeper.
Thus, there exists a need in the art for a mechanic's creeper design that provides a more comfortable, contoured fit for the user when lying down on the pads held between the side rails. Additionally, there exists a need in the art for a mechanic's creeper in which the caster assemblies are attached to the side rails without creating any protrusions on the top surface of the side rails and which also attach in a manner that prevents wear and tear to the bearings and the bearing races such as encountered with current mechanic's creeper designs. A need in the art also exists for employing an improved wheel design in the caster assemblies of mechanic's creepers.